| Abstract |
In areas where agricultural and stockraising industries are active, the efficient
and integrated management of high organic load waste that are produced is a
key factor for sustainability. Livestock and agricultural industries are in
operation without integrated sewage treatment plant and disposal areas, while
many industries are characterized by seasonal operation and low capacity.
Inadequate waste treatment and the uncontrolled disposal of waste to natural
recipients is the cause of serious environmental impacts. Eutrophication and
reduction of dissolved oxygen into the water recipient are among the most
common environmental problems are caused. The aim of this master thesis is
the search for an integrated management of high organic load waste through
a combination of processes, while its ultimate goal is to improve the
characteristics of the final discharge. In order to achieve the goal, the most
widespread farming waste of high organic load of the wider area of the
Prefecture of Heraklion was merged. The mixture contained piggery waste,
cheese dairy and food residues, which had been pre-treated by solar drying.
Anaerobic digestion, activated sludge (aerobic-anoxic treatment) and the
adsorption process using natural zeolite were used to process the mixture.
The systems were used in the logic of sequential arrangement of processes
and so the outflow of each system was the feed for the next. The main object
of the present research is the efficiency of zeolite and specifically of
Clinoptilolite as a final treatment of agricultural waste with the ion exchange
mechanism. Natural zeolite is a safe, thermally stable and economical
adsorbent material. Adsorption was carried out by two methods and for two
different granule sizes of zeolite. The first method was performed by stirring
the zeolite with the waste and the second by channeling the waste into zeolite
columns. In adsorption experiments, it was tested whether zeolite adsorbs
nutrients such as nitrogen and phosphorus or organic matter. The results that
were obtained were very positive. Initially, Anaerobic Digestion process
achieved 58% removal of total chemically required oxygen, 54% removal of
total solids and 64% removal of volatile solids, while for biogas the production
rate ranged from 0.7-0.9 liters per liter of reactor per day. Then, the process of
aerobic-anoxic treatment achieved, 30% removal of Chemically Required
Oxygen (COD) and 44% removal of total nitrogen (TN) was achieved. In
agitation experiments, in general, the granule size of zeolite 1.5-3 mm showed
to have a higher adsorption capacity than the granule size of zeolite <1 mm in
the long run. At the same time, granular zeolite with an adsorption rate of
95.3% and powdered with a rate of 94.4%, show high selectivity to phosphate.
In adsorption column studies, a gradual decrease in column efficiency was
observed during the passage of the treated volume. More specifically, the
column containing granular zeolite, after passing 1 L volume, had yields: 80%
TP adsorption and 40% TN adsorption while, after passing 4L from the
column it had yields: 48% TP adsorption and 11% adsorption TN. At the same
time, the results for the parameters of COD, phenols and NH3 showed that the
column had a stable adsorption. More specifically, after passing 1L and 4L,
the adsorption range was between 38-39% for phenols, 24-28% for COD and 91-93% for NH3. In addition, it was observed that while increasing hydraulic
load, the adsorption capacity of zeolite increases, the column with powdered
zeolite had a shorter lifespan compared to the column containing granular
zeolite and it seems that the adsorption using zeolite is satisfying for each
parameter and for each granule size of zeolite that was tested. Based on the
results, it is proposed to extend the adsorption column studies, as well as
elution experiments could be performed by using the saturated zeolite, in
order to monitor if the zeolite desorbs the adsorbed substances. Alternatively,
zeolite column regeneration experiments could be performed to assess
whether the zeolite can be reused for the treatment of livestock and
agricultural waste mixture.
|
Search
